[ltp] noise in audio on T430s

[Richard Neill]

On 26/09/13 13:56, Tamas Papp wrote:

> Does the UCA202 work with Linux?  If yes, was it difficult to get it
> working?  I have some bad experience with USB audio devices, but that's
> mostly from around 2006 and things may be plug & play now.

No trouble whatsoever. It just worked even when I bought it several 
years ago.

If it's your first time with multiple audio devices, you may find it a 
bit odd that you select the device from the volume-mixer, rather than 
the application. But Pulseaudio does then remember it. So for example, 
Amarok always goes to the USB audio, while system beeps always go to the 
builtin speakers.

>
>> Lastly, what kind of noise do you get? Is it hum, hiss, or interference?
>> The noise-cancelling headphones can also add a very high-pitched, quiet,
>> squeak (sounds like an analog TV flyback coil) sometimes.
>
> I get a quiet susurration, very similar to white noise.  It stops when I
> unplug the headphones from the T430s, so I guess that's the source.
> Also, when I scroll a PDF, I get a faint, irregular scratch-like noise.

That's what I hear. The white noise is just the various amplifiers being 
less than perfect. The "scratching" is the CPU going in and out of 
sleep, and the corresponding changes in load in the switch mode PSU, 
which inductively couples into the audio circuit.

Best wishes,

Richard